On Mon, Dec 7, 2015 at 8:29 AM, Robert Kierski <rkierski@xxxxxxxx> wrote: > I need some clarification on what data you want collected.... do you want iostat -xm collected before and after? Or at a periodic interval (1 sec)? > > I'm measuring sustained performance. This means I’m runnig for a period of time -- 1 minute. If you want iostat collected on an interval, that would probably be more data than one would want posted to this mailing list. > > But... yes, this is a RAID6. > > I've switched to HDD's as storage as there is concern on the list that the DDR disk devices could be causing unintended behavior in RAID6. With 6 HDD's, each able to do 270 MB/s on their outer edge, I'm getting RAID6 throughput of about 1080 MB/s when I use a thread count of 4, using FIO. > > -----Original Message----- > From: Dallas Clement [mailto:dallas.a.clement@xxxxxxxxx] > Sent: Friday, December 04, 2015 10:08 AM > To: Robert Kierski > Cc: Phil Turmel; linux-raid@xxxxxxxxxxxxxxx > Subject: Re: RAID 5,6 sequential writing seems slower in newer kernels > > Robert, is this with a RAID 6 array? Also, what are the actual throughput numbers you are getting? Would it be possible for you to capture the iostat -xm output and report the individual disk wMB/s and also the disk utilization for RAID 6? Hi Robert. Thanks for posting these results. Your fio direct I/O results look pretty darn good. Were you able to confirm with hdparm -t that you really can get 270 MB/s on your disks in reality? Also, what formula are you using to calculate best and worst case RAID 6 read and write speeds? > However, when I increase TC to 5, my TP is only 750 MB/s. When I increase TC to 32, my TP is about 250 MB/s. Now this is pretty disappointing. I agree, 12 cores should be able to easily handle this number of threads. -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
